Flyback converter is one of the most common types of power converters in low-power, switched-mode power supplies. They are widely used in, e.g., electronic gadgets, cell phones, notebook computers, and/or other types of consumer electronics, especially when galvanic isolation is needed between input power source(s) and output load(s). A flyback converter may comprise a primary coil and a secondary coil, which are electromagnetically coupled with each other. By controlling the flow of current through the primary coil using a switch (a metal oxide semiconductor field-effect transistor (MOSFET), for example), energy may be transferred from the power source (coupled to the primary coil) to the load (coupled to the secondary coil).
In practice, the primary and secondary coils may have an associated parasitic leakage inductance that also captures energy. The leakage inductance may cause additional losses unless its leakage energy is recovered. For consumer electronics, especially battery operated electronics, the energy recovery may become even more important because of limited power availability and thermal management challenges in miniaturized electronics. Another practical challenge is the mitigation of electromagnetic interference (EMI). Flyback converters, being operated by turning on and off switches, may generate EMI. Specific features in consumer electronics may place EMI constraints on a power supply of such device. For example, the “Multi-Touch” technology used with touch screens may demand low common-mode noise within specific frequency band(s). Such requirements may require flyback converters to be operated at appropriate fixed switching frequencies. Therefore, the inventor has recognized the need for a flyback converter capable of recovering the leakage energy in high efficiency and operable with fixed switching frequencies.